Add GET /fs/browse directory-listing endpoint

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/web/settings_handlers.go

@@ -2,6 +2,9 @@ package web
 
 import (
 	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
 
 	"antidrift/internal/settings"
 
@@ -61,3 +64,57 @@ func (s *Server) handlePostSettings(c *gin.Context) {
 	s.broadcast()
 	c.JSON(http.StatusOK, req)
 }
+
+type browseEntry struct {
+	Name  string `json:"name"`
+	Path  string `json:"path"`
+	IsDir bool   `json:"is_dir"`
+}
+
+type browseResponse struct {
+	Dir     string        `json:"dir"`
+	Parent  string        `json:"parent"`
+	Entries []browseEntry `json:"entries"`
+}
+
+// handleBrowse lists subdirectories plus .md files under dir, so the UI can build
+// a file picker that returns a real server-side path. Dotfiles are NOT hidden —
+// the default profile lives under ~/.antidrift. Localhost-only daemon; no jail
+// beyond OS permissions (same trust boundary as the rest of the UI).
+func (s *Server) handleBrowse(c *gin.Context) {
+	dir := strings.TrimSpace(c.Query("dir"))
+	if dir == "" {
+		dir = s.browseStart()
+	}
+	dir = filepath.Clean(dir)
+	infos, err := os.ReadDir(dir)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+	resp := browseResponse{Dir: dir, Parent: filepath.Dir(dir), Entries: []browseEntry{}}
+	for _, e := range infos {
+		name := e.Name()
+		full := filepath.Join(dir, name)
+		if e.IsDir() {
+			resp.Entries = append(resp.Entries, browseEntry{Name: name, Path: full, IsDir: true})
+		} else if strings.HasSuffix(name, ".md") {
+			resp.Entries = append(resp.Entries, browseEntry{Name: name, Path: full})
+		}
+	}
+	c.JSON(http.StatusOK, resp)
+}
+
+// browseStart picks the directory of the current knowledge path, else $HOME.
+func (s *Server) browseStart() string {
+	s.settingsMu.Lock()
+	kp := s.settings.KnowledgePath
+	s.settingsMu.Unlock()
+	if kp != "" {
+		return filepath.Dir(kp)
+	}
+	if home, err := os.UserHomeDir(); err == nil {
+		return home
+	}
+	return "/"
+}